Quote:
Originally Posted by jr_tech
Barkhausen oscillation? Perhaps try holding a strong magnet close to the horizontal output tube to see if the pattern changes. Just a WAG, I have never observed BO.
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I believe that I observed it in my Hallicrafters T-67:
The interference is seen as squiggly vertical lines running down through the reporter's face. It disappeared after I replaced the 6BG6T horizontal output tube, just as suggested in an old service book. The book noted that Barkhausen's is more prominent with weak signals than strong ones.
Another solution is to place a small circular magnet around the tube. The DuMont RA-103 has a little magnet mounted inside the HV cage to suppress Barkhausen's.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html